It could just be a curious one-off problem. These things do seem to happen very occasionally, for reasons I can't work out (it claims to have successfully sent the file, the file's in the right place etc.). Anyway, I'll send the file manually to Falkor now, and if it happens again we'll have to think more.
I didn't get the turn file either. Turns out my spam filter was deleting the message right away instead of moving it to the spam folder. I did receive the first two turns without a problem, though.